1. Field Of the Invention
The invention relates to a brake system with at least one brake circuit, actuated by a feeding of a brake pressure, with a mechanical brake-pressure control device and an electrical brake-pressure control device.
2. Brief Description of the Background of the Invention Including Prior Art
Such a brake system is actuated predominantly by the electrical brake-pressure control device. In case of a fault in the electrical brake-pressure control device, the brake system remains functioning based on the redundant brake-pressure transmitted by the mechanical brake-pressure control device.
Such a brake system is known from the German Patent Document herein incorporated by reference DE-OS-3,501,179-Al. The brake-pressure modulator of this brake system is formed as a blockin device with respect to the redundant brake pressure. For this purpose, the brake-pressure modulator of the German Printed Patent Document, herein incorporated by reference, DE-OS-3,501,179-Al is structured such that, upon actuation of the brake system in the sense of an increasing or level-maintaining brake pressure, its passage is blocked for the redundant brake pressure and, upon actuation in the sense of a falling brake pressure, its passage is open. Thereby, the desired brake-pressure drop is made possible by means of the mechanical brake-pressure control device.
If the known brake system is to comprise one or several elements, which require a particularly quick brake-pressure drop, then the brake system has to contain an electrically controlled valve device, as taught for example in FIG. 2 of the German Printed Patent Publication, herein incorporated by reference DE-OS-3,501,179-Al. This electrically controlled valve device assures the required quick brake-pressure drop during operation of this element or these elements, respectively. Such elements are, for example, an anti-skid protection system and a superposed electrical or hydraulic long-time brake, conventionally designated as retarder.
The German Printed Patent Document DE 3,212,930 to Werner Stumpe, herein incorporated by reference, teaches a multi-circuit braking system. A pressure control valve is employed which, on the one hand, assures that the control circuits are always in use and that the pressures furnished to the brake cylinder compensate in each case.
The German Printed Patent Document DE 2,218,315 to Joseph R. Morse et al., herein incorporated by reference, teaches a braking system for a vehicle. A control unit is furnished by an electronic signal processing unit which delivers electrical output signals, and is connected to a braking valve or to brake cylinders and coordinated to pressure indicators. This electronic signal processing unit compares the signal corresponding to the momentary pressure values present in the brake control valve and in the brake cylinders.
The German Printed Patent Document 1,555,556 to Heinz Nicolay et al., herein incorporated by reference, teaches a pressure operated braking system for vehicles, as well as a relay valve and a solenoid valve for the switching on of a retarder. A relay valve is constructively combined with a solenoid valve such that the double valve body of the relay valve can also be actuated by a piston subjectable to a pressure controlled by the relay valve.
The German Printed Patent Document DE 3,703,639 to Werner Stumpe, herein incorporated by reference, teaches an electro-pneumatic braking system for tractors. An emergency brake release device is furnished, which can be activated in case of an intereruption of a brake line by electrical and/or pneumatic signals generated by an activation of a brake-Pedal
The German Printed Patent Document DE 3,240,276 to Ewald Hubl et al., herein incorporated by reference, teaches a pressure control valve for a braking system. The reference employs a solenoid valve disposed at least indirectly analog relative to the brake cylinders for controlling the brake pressure, where the solenoid valve is continuously adjustable depending on the current fed to the solenoid valve.
The German Printed Patent Document DE 3,205,228 to Egbert Muller et al., herein incorporated by reference, teaches a multi-circuit braking system based on a pressurized medium. The pressure control valve of the reference is controlled from several circuits and includes electrical switches for at least one control circuit.
The German Printed Patent Document DE 3,416,338 to Gerhard Fauck et al., herein incorporated by reference, teaches an apparatus for the adaptation of the distribution of the brake force. A delay valve allows the pressure to pass with a value level reduced by the opening pressure in case of a further increasing pressure, once the opening pressure has been reached.
The German Printed Patent Document DE 3,239,970 to Ingolf Grauel et al., herein incorporated by reference, teaches a braking system for a vehicle train. The brake value sensor is formed for controlling both, electrically-actuated and pressure-actuated braking circuits. One of the pressure-activated circuits for controlling the trailed control valves is a pure control circuit.
The German Printed Patent Document DE 2,939,907 to Erich Reinecke, herein incorporated by reference, teaches a dual-circuit braking system. An adapter valve is employed between the control connection for the subjection of the second part face and the conduit carrying the pressure for the rear-axle brake circuit.
The WABCO pocket book addition, published in 1987 illustrates on page 241 a load/empty valve.